OAKDALE, Minn. — Police were still trying to determine Tuesday why a 34-year-old man randomly shot at passing vehicles in a suburban St. Paul neighborhood, wounding a female driver and killing her 9-year-old son, an aspiring astronaut whom she'd just picked up from daycare.

A witness told The Associated Press that the man, whom police identified Tuesday as Nhan Lap Tran of Oakdale, was nonchalantly walking down the block the night before, as if he was on a stroll, when he began firing.

Devin Aryal, 9, of Oakdale was killed. His mother, Melissa Aryal, 39, was shot in the arm. A woman in another vehicle also was injured, but was expected to survive.

Police Chief Bill Sullivan said it appeared Tran legally owned the handgun used in the attack, and that authorities are not aware of any mental health issues he may have. Sullivan said officials were trying to determine if something happened to trigger the shootings.

"At this particular point in time it appears to be completely random," Sullivan said.

Sullivan said Tran was arrested Monday after police responded to the neighborhood on a report of shots fired. Tran was arrested about a half-mile away from where the shooting started, and was in custody Tuesday on suspicion of second-degree murder and first-degree assault. Prosecutors expected to file charges Wednesday.

Sullivan said Tran does not have a history with Oakdale police. Tran did not have a criminal history, according to online court records.

Cheryl Russell, 55, lives across the street from the house where police said Tran lived for several years. She said she was sitting on her couch around 6 p.m. Monday when she looked out her bay window and saw a short, stocky man in dark clothes walking down the street.

She heard popping noises, which she thought were from firecrackers.

Moments later, Russell said, her son shouted from upstairs that a man was outside shooting at cars. Russell peered out the window to see flashes from the gun as the man fired. She watched as he walked up the hill and out of sight, still shooting at cars. She said she heard about 15 shots.

"He was nonchalant," Russell said. "Just walking like he was out for a stroll. It was crazy."

Police were on the scene in minutes, she said. Russell said she didn't recognize the gunman.

Sullivan said Tran was arrested without incident when an officer confronted him. He was found with a handgun near him and a "substantial" number of rounds of ammunition, Sullivan said.

On Tuesday, detectives combed a six-block area for spent gun casings and additional gunfire damage. Sullivan said four vehicles were shot.

Melissa Aryal told the AP that she picked up her son, Devin, from daycare Monday evening and was heading home when she heard a noise that sounded like something under the hood of her minivan. Aryal pulled up to a stop sign, turned the corner, and was hit in the arm by a bullet.

While injured, she drove to the parking lot of a nearby Rainbow Foods then noticed Devin was slumped over, also shot. She says she held him until an ambulance arrived, but he died of his injuries.

"He didn't deserve this. He was just a baby," she said.

A 68-year-old woman in another vehicle also suffered multiple gunshot wounds but was expected to survive, Sullivan said.

Devin Aryal was a fourth-grader at Oakdale Elementary School, a school of about 500 students. A team of social workers and psychologists was talking with students Tuesday. District 622 spokeswoman Jennifer McNeil said students are shaken up and "some of the kids are taking it pretty hard."

Meanwhile, a small group of about 10 people huddled in prayer at the Rainbow Foods parking lot Tuesday to pray for the victims. The Rev. Chris Duckworth led the group, and read Psalms of Lament: "Psalms where the people are crying out, `Why God? Why?'" Duckworth said.

Duckworth, a senior pastor at Grace Lutheran Church in St. Paul, said he didn't know any of the victims, but knew he had to give people a chance to grieve.

"Frankly, I didn't know what else to do," he said.

Melissa Aryal cried as she talked about Devin, whom she described as a happy-go-lucky boy who loved soccer, math and science. She said he was a good student, and liked science because it gave him a chance to tinker – take things apart and put them back together. He dreamt of growing up to be an astronaut.

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